1. Field of the Invention
The present invention relates to a self-locking belt reel-in mechanism for safety belts, especially of automobiles or other motor vehicles; the mechanism has a housing, and a belt reeling-in shaft which is mounted therein in such a way that it cannot be displaced axially, but can be displaced radially under the effect of locking forces; the ends of the belt reeling-in shaft extend through openings of the housing, and are each provided, in the plane of its opening, with an arrangement which provides for arresting the belt reeling-in shaft; one of these arresting arrangements engages a fixed internal toothing of one of the openings when locking forces occur which do not exceed a predetermined value, and when locking forces occur which exceed the previously mentioned locking forces, both arrangements engage fixed internal toothings of both of the openings, so that arresting, and hence locking, of the belt reeling-in shaft results either at one end or at both ends of the latter.
2. Description of the Prior Art
One known belt reel-in mechanism of this general type (according to U.S. Pat. No. 4,509,707 Ernst et al. issued Apr. 9, 1985 and belonging to the Assignee of the present invention) discloses a two-sided locking of the shaft; locking is differentiated for basically two different load situations, namely the so-called normal situation and the so-called crash situation. If the belt strap force does not exceed a standard value, as occurs, for example, when the vehicle is braked in an everyday traffic situation, the locking action of a locking member disposed on one side of the belt reeling-in shaft suffices in order to restrain the safety belt and the person who is strapped in. However, if far greater belt strap forces which exceed the normal occur during a collision or the like, after the locking member has caught, such great tension forces, and therefrom radial forces acting on the shaft or on the winding, become effective that they shift the shaft as a whole radially and thereby also cause engagement of the arresting mechanism at the other end of the shaft With the heretofore known belt reel-in mechanism, the locking member comprises a member which is mounted in a recess of the associated opening in the housing, and can be pivoted into the toothing of a toothed wheel which is aligned therewith, with an actuating element in the form of a pin, which is controlled by the self-locking mechanism, being disposed on the member. Thus, the member fulfills a double function, because on the one hand it is in itself a locking element for the normal load situation, and on the other hand during an accident brings about an additional locking in that it effects the deflection of the shaft and hence its two-sided locking by engagement of the two-sided toothed wheel into the internal toothing of the openings of the housing. In this arrangement, the toothing of the opening on that side of the housing facing the member can be limited to a sector of the periphery, and the belt reeling-in shaft can be mounted externally of the housing on lateral housing covers (see also U.S. Pat. No. 4,223,853 Ernst issued Sept. 23, 1980 which also belongs to the Assignee of the present invention).
With the previously described known belt reel-in mechanism, a so-called thrust ring for absorbing load is not required, since the walls of the housing are functionally utilized for this purpose. A somewhat similar situation also exists with a further known belt reel-in mechanism (German Offenlegungsschrift No. 26 46 238), according to which a respective toothed wheel is disposed at both ends of the belt reeling-in shaft; corresponding inner toothings in the openings of the housing are associated with these toothed wheels. The effect connected with this is that the shaft, which shifts radially in the housing when locking forces occur, can be supported on both sides of the housing, and that accordingly the housing is loaded symmetrically and essentially free of distortion. As a result, the walls of the generally U-shaped housing can be lighter in weight, and a smaller structural width of the belt reel-in mechanism is also provided. To mount the shaft, the latter has, on both ends, shaft journals which are resiliently supported in radial direction in associated bearings. This resilient mounting is a portion of the belt-strap-sensitive locking mechanism which responds during accelerated withdrawal of the belt strap. Due to the dependence of the accelerations which occur relative to the size of the belt strap winding, the ratio of the radial forces required for the locking to the effective spring forces at the bearings of the shaft are not constant, and therefore no exactly definable locking can be achieved with this known belt-locking mechanism.
An aligned arrangement of the toothed wheels in the openings of the sides of the housing is also provided by a known belt reel-in mechanism disclosed in German Offenlegungsschrift No. 28 32 160, while in German Offenlegungsschrift No. 31 20 379, although it discloses a belt reel-in mechanism having two-sided locking and a shaft which can be shifted transversely for this purpose, the two-sided toothed wheels are, in this case, not disposed in openings of the housing, but rather are disposed within the sides of the housing, and the arresting is effected against inwardly flanged housing tangs, so that at any given time only one tooth of the toothed wheels can be effective. A principally similar situation results from German Offenlegungsschrift Nos. disclosures 15 31 545 and 15 31 546, and also from U.S. Pat. No. 3,695,545 Peters dated Oct. 3, 1972. Great Britian Pat. No. 14 28 111, and U.S. Pat. No. 3,876,164 Dully dated Apr. 8, 1975 are also relevant in this respect, while the subject matter of U.S Pat. No. 3,074,761--Ryan dated Jan. 22, 1963, entitled Safety Seat Belt, Janguart dated May 15, 1962 provides for an arresting with three teeth when the belt reeling-in shaft is shifted radially by virtue of pulling of the belt strap.
An object of the present invention is to provide a self-locking belt reel-in mechanism of the aforementioned general type, which is designed for two fundamentally different locking situations, namely for locking in the everyday "normal operation" on the one hand, and for locking in the high-load situation (crash) on the other hand. During normal operation, the belt reel-in mechanism should operate with few moving parts, should be able to be constructed small and if possible symmetrically, and should be able to be produced at low cost.